1. Field of the Invention
The present invention relates to an information processing device and method and program, and in particular relates to an information processing device and method and program that can more appropriately perform gamut conversion of content.
2. Description of the Related Art
Heretofore, a method using sRGB color space, which is a standard color space for monitors, has been used as a color space to express RGB data. For example, on a personal computer, upon JPEG (Joint Photographic Experts Group) data that is generally used being opened, the sYCC data that is recorded in the JPEG data is immediately converted to sRGB data. If there is data outside the sRGB gamut (i.e. negative value or value of greater than 256 of an 8-bit value) in the sYCC data, a natural clip to sRGB color space occurs, and color distortion can occur.
A natural clip indicates a phenomenon whereby a color outside the gamut of the image data supplied externally is forcibly expressed with the colors in the gamut of the device. For example, in the case that only the R-component of a certain color expressed with RGB is greater than the maximum value of the R-component of the gamut, the R-component of the color is expressed with the maximum value of the R-component in the gamut (natural clip). At this time, the RGB balance of the original RGB becomes off-balance due to natural clipping, and the hues change. This kind of hue change is called “color distortion”. That is to say, the color expressed is different than the original color, so this kind of color distortion is not desirable.
In order to prevent this, there is a method to perform gamut conversion beforehand to compress the gamut of the image data on the recording device side to the sRGB gamut beforehand. With this gamut conversion, the original sYCC data has already been compressed to the sRGB gamut, whereby even when the JPEG data is opened and converted to sRGB, data outside the gamut is not generated. That is to say, the occurrence of the above-described color distortion can be suppressed.
However, sRBG represents the gamut of a standard personal computer monitor, but when compared to a printing device or wide gamut liquid crystal television receiver (wide gamut liquid crystal TV), there are clearly portions that are narrow.
FIG. 1 is a schematic diagram showing a comparison state of gamut ranges. As in the example shown in FIG. 1, the gamut 1 of a general inkjet printer is narrower than the sRGB gamut 2 in many hues, but is wider only for many blue/green regions. Also, generally, the color gamut 3 of a wide gamut liquid crystal TV is wider than the sRGB gamut 2 in all hues.
However, once a gamut of picture content is converted to a narrow sRGB gamut, the originally recorded information before compression is lost. This information is inexpressible, regardless of the gamut of the output device, even with a wide gamut liquid crystal TV which has a wide gamut. That is to say, by converting the gamut to a narrow gamut, the image quality of the picture content may deteriorate unnecessarily.
Therefore, various proposals have been given for methods to restore the data that has been compressed once and to recompress to the gamut of the output device (e.g., see Japanese Unexamined Patent Application Publication No. 09-9082 and Japanese Patent No. 4061907 (corresponding to U.S. Pat. No. 7,130,462)).
Japanese Unexamined Patent Application Publication No. 09-9082 discloses a method whereby, in the event of printing barcode information showing profile data to paper together with an image, and printing with a separate printing device, the gamut is recompressed for use with another printing device by scanning the barcode information.
Also, Japanese Patent No. 4061907 discloses a method whereby information before compression of the compressed RGB data (maximum/minimum values, compression table, etc) is read in, image data is restored, and the gamut is recompressed for the final output device.